Monosodium urate, calcium pyrophosphate dihydrate (CPPD) and silica crystals abosrb chiefly IgG and an alpha 2 macroglobulin from normal human serum. Crystals with adsorbed IgG show enhancement of phagocytosis by human polymorphonuclear leukocytes (PMN) and induce the platelet release reaction. Efforts will be made to identify urate crystals in atheromatous plaques and to determine the effects of other biologically available adsorptive substances (e.g. from PMN) that might block IgG adsorption and so explain the switch on-off mechanism of gout and pseudogout. A more sensitive assay for inorganic pyrophosphate will be used to quantify this substance in cells, natural and cultured, from patients with CPPD deposition and control subjects as part of a search for a biochemical marker for the disease as well as a search for causes of increased cellular PPi production (or underdestruction). Lastly, the degree of saturation of synovial fluids with PPi will be determined with the possibility of therapeutic manipulation of joint fluid PPi levels leading to CPPD crystal removal. BIBLIOGRAPHIC REFERENCES: Kozin, Franklin and McCarty, Daniel J.: Protein binding to monosodium urate monohydrate, calcium pyrophosphate dihydrate and silicon dioxide crystals: Physical characteristics. In Symposium on Pseudogout and Pyrophosphate Metabolism Arthritis Rheum, 19: (in press), 1976 suppl. Camerlain, Monique, McCarty, Daniel J., Silcox, Donald C., and Jung, Andre: Inorganic pyrophosphate pool size and turnover rate in arthritic joints. The Journal of Clinical Investigation, 55-1373-1381, 1975.